The main approaches to flame retarding polyamides are melt additives, topical finish treatments, and copolymerization with flame resistant monomers. Melt additives generally include halogenated organic compounds with high levels of bromine or chlorine. A second component when halogenated compounds are employed is antimony trioxide (Sb.sub.2 O.sub.3). Other popular elements found in melt additives are phosphorous and molybdenum. The melt additive approach has found limited utility in polyamide fibers due to the necessary high loadings, discoloration of polymer with some phosphorous and molybdenum compounds, and high smoke generation due to brominated compounds. Finish treatments generally require high add-on levels, and many of these lack the durability to cleaning procedures required for polyamide fabrics such as carpeting. Copolymerization is an effective way to produce flame retardant polymers; however, many of these are not considered fiber spinning grade.
U.S. Pat. No. 3,829,400 discloses a flame retardant polyamide fiber composition using an oxy-tin compound and a halogen as flame retardant agents.
U.S. Pat. No. 4,141,880 discloses a flame retardant nylon composition which contains a condensation product derived from brominated phenol.
U.S. Pat. No. 4,064,298 discloses a flame retardant polyamide fiber containing zinc borate and an organic halide.
U.S. Pat. Nos. 4,116,931 and 4,173,671 disclose flame retardant fibers and carpets which contain complex salts such as metal borocitrates or borotartrates.
An object of the present invention was to provide a polyamide fiber with improved flame retardancy which is halogen-free, antimony-free and phosphorous-free.
Another object was a method of producing such polyamide fibers. Still another object was a carpet with improved flame retardancy.